Electrochemical biosensor for DNA methyltransferase detection based on DpnI digestion triggering the formation of G-quadruplex DNAzymes

Aberrant DNA methylation, which is caused by the abnormal level of DNA methyltransferase (MTase), has been considered associated with a growing number of human diseases. Although there are various methods paying close attention to DNA methyltransferase (MTase) detection, most of them are generally complex and expensive. Here, a simple electrochemical strategy for sensitive detection of DNA methyltransferase (MTase) and inhibitor screening based on DpnI digestion triggering the formation of G-quadruplex DNAzymes has been developed. In this paper, a probe richness of guanine (G) was first self-assembled on the surface of the electrode through Au-S bond and then hybridized with the complementary DNA. Without DNA methylation, G-quadruplex DNAzymes cannot be formed due to the double helix structure and a weak electrochemical response can be observed. On the contrary, an obvious enhancement of the electrochemical response can be achieved after the cleavage of the methylated double-strand DNA by DpnI since G-quadruplex DNAzymes can be obtained, which catalyze the oxidation of hydroquinone by H2O2 with the assistance of the cofactor hemin. This method is under a detection limit of 0.96 U/mL and can monitor the change of DNA methylation level selectively. Moreover, RG108 was selected as a representative inhibitor for studying the inhibition activity of DNA MTase.